In the Washington Post, Carolyn Butler reports on some research that will seem pretty familiar to anyone who's been following the recent trend towards positive thinking as medicine:

A recent study published in the journal Circulation showed that a sunnier outlook on life is associated with a lower risk of heart disease and mortality. The research, which tracked more than 97,000 women older than 50 for eight years, found that optimists were 9 percent less likely to develop heart disease and 14 percent less likely to die from any cause than their pessimistic counterparts. Those with a high degree of "cynical hostility" were 16 percent more likely than all others to die during that same period.

"Cynical hostility" certainly does sound bad, for your friends and family if not for your heart. But what's most likely to keep the ol' CH at bay? Turns out it's: money. Butler writes, "socioeconomic status was strongly tied to level of optimism: The women with the most-positive outlook on life tended to be wealthier, more educated, in better shape and less likely to smoke or to be overweight." Still, optimism was apparently correlated with health even after controlling for cold hard cash, leaving study authors to puzzle yet again over what gives glass-half-full types greater longevity. Butler notes the now-popular theory "that your psychology has a direct effect on physiology, impacting blood pressure, heart rate, stress hormone levels and immune function, all of which can contribute to disease and mortality." But she also quotes cardiologist Elizabeth Klodas, who asks,

Is it the chicken or the egg? Are you a better patient because you have an intrinsic optimistic attitude, or do you become more optimistic because your outcomes are better because you're following a regimen that's actually helping you get better?

And, says study author Hilary Tindle, "On the one hand it seems intuitively obvious, but we're not there yet in terms of the evidence we need in order to say optimism causes better health outcomes. All we can say now is that optimism is associated with better health outcomes, but without following people over a lifetime, we can't say which came first." It may seem "intuitively obvious" that positive thinking makes you healthier, but it's also pretty obvious that being healthy — or at least responding well to treatment — makes you happier. Some researchers may have figured out how to separate these effects, but it does seem that many studies of positive thinking and illness would suffer from the same problem: wouldn't people who start to get better naturally feel more positive? And, in a more general way, might people who have good jobs, stable finances, and happy relationships feel more optimistic? Might optimism be the result of a good life, not the cause?

Klodas says "there are many positives to being more positive," and it's true that an optimistic outlook can sometimes make a bad situation seem better, or provide the necessary confidence to help someone out of a rut. But Klodas's chicken-or-egg caveat makes it clear that we are far from being able to prescribe positive thinking as any sort of cure-all. This is no reason people shouldn't be optimistic if they want to, and if they can. But it is evidence that maybe we shouldn't saddle sick people with the added pressure to be sunny.